Biotin intermediate



Patented Jan. 25, 1949 c UNITED STATES PATENT OFFICE BIOTIN INTERMEDIATE Stanton A. Harris, Westfield, and Karl Folkers, Plainfield, N. J assignors to Merck & 00., Inc., Rahway, N. J a corporation of New Jersey No Drawing. Application September 16, 1944,

Serial No. 554,453

18 Claims. (Cl. 260-329) 1 2 This invention is concerned generally with H novel chemical compounds and processes of prelcaialyst paring the same; more particularly it relates to novelcompounds useful as intermediates in syn- R R00 thesis of the growth-promoting factor, biotin. 5 I\IIH NH Biotin is known to be one of the isomers of the A: chemical compound 2- (4' carboxy-butyl) 3:4- ureido-tetrahydrothiophene, having the empirical om-s-omonmo 02R formula C1oH16O3N2S, and the structural formula: 10 l 011-, then H+ HN( lNH 1 am NH: no CH H2-S( JHCH2CH2CH2OH2COzH C S-CH(CHZ)4 2 It is now found that this compound can be syn- 0 OX thesized by reactions indicated as follows:

I IH, ITIH: O cnoo H GHCO H K052660211 A 2 1|1NCNH GHQ-SH Hr-S--CH2CO2H OH .CH

(1) (2) (3H-SC1H (CH2) lo 02H 12 1 In the above formulae, R represents an alkyl, 300x 5 aryl or arylalkyl group; X, a halogen; and M an R00 R00 alkali metal or an alkaline earth metal.

| The reactions above indicated are conducted 1 a T as follows: 2-amino-3-mercapto-propanoic acid (DH-002R err-002 (1) and chloroethanoic acid are condensed in (QHFSAJHZCOSR m an alkaline aqueous solution to form 2- amino-' 3-carboxymethyl-mercapto-propano1c acid (2); (4) (3) which is then treated with an acylating agent, such as an acyl halide, in an aqueous alkaline l solution to yield 2-acylamido-3-carboxymethylmercapto-propanoic acid (3). This product is RC0 esterified using a mineral acid catalyst to pro- NH O NH 0 duce the diester (4) of the acid (3), and the dies- 15 5 ter is treated; with alkali metal alcoholate orkai J II G 02R ea a kalme ear h metal alcoho ate or an al a 1 40 metal or the Z-alkaline earth metal deriva- M tive of an ester of 2-carboxy-3-keto-4-acylamidotetrahydrothiophene (5). This compound, when 5 U l heated with a dilute mineral acid, is hydrolyzed and decarboxylated to produce 3-keto-4-acylamia do-tetrahydrothiophene (6) which, when reacted NH NOH N'Hr-OH NH 0 with 4-carboxybutanal ester in a lower aliphatic J P alcohol reaction medium containing piperidine l and a lower aliphatic carboxylic acid, produces 2- (4-carboalkoxy-butylidene) 3-keto-4-acylamido-tetrahydrothiophene ('7). This product, when reacted with hydroxylamine yields as ester of the lmoono corresponding oxime, 2-(P-carboxy-butylidene) 3-isonitroso-4 acylamido tetrahydrothiophene R00 R00 R00 R00 (8) which upon treatment with a mixture of zinc, 1 1 NH 11111 a lower aliphatic acid and a lower aliphatic acid anhydride, produces an equilibrium mixture of CH CH H 2-(4'-carboxy butylidene) -3 :4 di(acylamido) tetrahydrothiophene ester (9a) and 2-(4-car- (9a) (9b) boxy-butyl) -3:4-di(acylamido) -4:5 dihydrothiophene ester (9b). This equilibrium mixture, or

tetrahydrothiophene (11) which, when reacted 1 with a carbonyl halide, produces the compound 2- (4'-carboXy-butyl) -3 :4-ureido tetrahydrothiophene. of stereoisorners, one of which is racemic biotin, from which upon resolution, is obtained the dextrorotatory isomer, biotin.

This invention is concerned generally with the class of compounds of which intermediate 8 above is a member, namely 2-(omega-carboxy-alkylidene)-3-isonitroso-4-acylamido tetrahydrothiophenes, and esters thereof represented by the general formula:

m-sh;on cm ,,oonv

wherein R. is an acyl group, R is selected from the class consisting of hydrogen alkyl, aryl and arylalkyl groups, and n is a small integer. More specifically, the invention is concerned with compounds of the above formula wherein n is 3, the esters of 2-(4'-carboxy-butylidene) -3-isonitroso- 4-acylamido-tetrahydrothiophenes.

According to the present invention, compounds of the above general formula are prepared by reacting hydroxylamine or a hydroxylamine salt with an ester of 2-(omega-carboxyalky1idene) 3-keto-4-acylamido tetrahydrothiophene. Corresponding acids are obtained by hydrolysis of the esters thus produced. The compound used as starting material is obtained by the process outlined above and described in detail in concurrently filed applications, Serial Nos. 554,458, 554,449, now Patent 2,437,719, 554,450, 554,- 451, and 554,452. When hydroxylamine or a salt thereof is reacted with an ester of 2- (4-carboxy-- butylidene)-3-keto-4-acylamido tetrahydrothiophene, the product obtained is an ester of 2- (4'-carboxy butylidene) -3 isonitroso 4-acylamido-tetrahydrothiophene, an intermediate useful in synthesis of biotin as described in concurrently filed applications, Serial Nos. 554,454, 554,- 455, 554,456, and 554,457.

The following examples illustrate methods of carrying out the present invention, but it is to be understood that these examples are given by way of illustration and not of limitation.

( nnz-s-momcmncogona About 2.3 g. of 2-(3-carbonmethoxy-propylidene) -3-keto-4-benzamido tetrahydrothioph'ene are added to a solution of approximately 0.75 g. of hydroxylamine hydrochloride in 15 cc. of pyridine, and, after standing about 16 hours at room temperature, the mixture is diluted with about 4 volumes of water and extracted with chloroform. The chloroform extract is cooled, washed at below C. with hydrochloric acid (1 N), then with water, and dried. Upon evapora- This product is obtained as a mixture 1 4 tion of the chloroform the product, 2-(3'-carbomethoxy propylidene) 3-isonitroso 4 benzamido-tetrahydrothiophene is obtained as an oil which is purified'by recrystallization from methanol and other to obtain the pure product (M. P. 1138-167 C.).

H -'SC:CH(CH2):COCH: Abouttl332 g. of 2'-(4 carbomethoxy-butylidene). 3-keto-4-benzamido-tetrahydrothiophene and about 2.80 g. of hydroxylamine hydrochloride are dissolved in alcohol and mixed with about 50 cc. of dry pyridine. The mixture is allowed to stand about hours at C., then it is diluted with four volumes of water and extracted with chloroform. The chloroform 'extract is cooled, shaken with hydrochloric acid (2.5 N), washed by shaking with water, dried and concentrated at 40 C. Upon evaporation of the solvent a mass is obtained which is extracted with ether to remove impurities, and dried. The crude 2-(4"-carbomethoxybutylidene) '3 -lSO1'll-t' troso-4- benz-ylam'idotetrahydrothiophene thus obtained (M. P. 129138 C.) is purified by repeated recrystallization from methanol, yielding the pure oxime (M. P. 1 59460 0.). When the pure oxime is treated with alcoholic sodium hydroxide, then with aqueous acid, 2-4'-carboxy-butylidene) -3-isonitroso-4-benzamido tetrahydrothiophene (M. P. 203-4 C.) is obtained.

3-isonitroso- 4-benzamidotetrahydrothiophene (M. P. -14 C.)

It will be understood by persons versed in this field of invention that the above-described reactions can be conducted using as a starting material a compound within the general class of the 2-(omega-carboxy-alkylidene) 3-keto-4-acylamido-tetrahydrothiophene esters but having an acylamido group diiferent from benzamido, for" example acetamido starting materials yield corresponding acetamido products, propamido starting materials yield propamido products, etc. The ester group; not being involved in'or affectedby the reaction, can be any alkyl, aryl or arylalkyl ester and a corresponding product is obtained,

The product obtained is 2-(5'-carbothoxy-pentylidene) viz., propyl ester starting material yields propyl ester product, benzyl ester starting material yields benzyl ester product, etc.

Modifications may be made in carrying out the present invention without departing from the spirit and scope thereof and the invention is to be limited only by the appended claims.

What is claimed is:

1. A compound selected from the class consisting of aryl, alkyl and arylalkyl esters of 2- (omega-carboXy-alkylidene) 3 isonitrosoiacylamido-tetrahydrothiophene.

2. Alkyl esters of 2-(3-carboxy-propylidene) 3-isonitroso-4-acylamido-tetrahydrothiophene.

3. Alkyl esters of 2-(5'-carboXy-pentylidene)- 3-isonitroso-4-acy1amido-tetrahydrothiophene.

4. Alkyl esters of 2-(4'-carboxy-butylidene) -3- isonitroso-4-acylamido-tetrahydrothiophene.

5. Lower alkyl esters of 2-(l-carboxy-butylidene) -3-isonitrosol-acylamido tetrahydrothiophene.

6. The ethyl ester of 2-(3'-carboxy-propylidene) -3isonitroso-d-benzamido-tetrahydrothiophone.

'7. The methyl ester of 2-( i'-carboXy-butylidene) -S-isonitroso--benzamido -tetrahydrothiophene.

8. The ethyl ester of 2-(5'-carboxy-pentylidene) -3-isonitr0so-4-benzamidctetrahydrothiophene.

9. The process that comprises reacting a substance selected from the class consisting of hydroxylamine and salts thereof with a compound selected from the class which consists of alkyl, aryl and arylalkyl esters of 2-(omegacarboxy-alkylidene) -3-keto-'=-acylamido tetrahydrothiophene to produce the corresponding 3- isonitroso compound.

10. The process that comprises reacting a sub stance selected from the class consisting of hydroxylamine and salts thereof with an alkyl ester of 2-(3-carboxy-propylidene) 3 keto-4- acylamido-tetrahydrothiophene to produce the corresponding 3-isonitroso compound.

11. The process that comprises reacting a substance selected from the class consisting of hydroxylamine and salts thereof with an alkyl ester of 2-(4-carboxy-butylidene) 3 -keto-4-acy1amido-tetrahydrothiophene to produce the corresponding 3-isonitroso compound.

12. The process that comprises reacting a substance selected from the class consisting of hydroxylamine and salts thereof with an alkyl ester of 2-(5-carboxypentylidene 3 ketolacylamide-tetrahydrothiophene to produce the corresponding 3-isonitroso compound.

13. The process that comprises reacting a sub stance selected from the class consisting of hydroxylamine and salts thereof in a pyridine solvent with 2-(4' carbomethoxy butylidene) 3-keto-4-benzamido-tetrahydrothiophene to produce the corresponding 3-isonitroso compound.

14. The stereoisomer of 2-(4-carbomethoxybutylidene)-3-isonitroso 4 benzamido tetrahydrothiophene having, when in substantially pure form, a melting point of C.

15. Alkyl esters of 2-(4'-carboxy-alkylidene)- 3-isonitroso-4-acylamido-tetrahydrothiophene.

16. The process which comprises reacting a substance selected from the class consisting of hydroxylamine and salts thereof with an alkyl ester of 2-(omega-carboxy-alkylidene) -3-keto-4- acylamido-tetrahydr0thiophene to produce the corresponding 3-iso-nitroso compound.

17. The process which comprises reacting a substance selected from the class consisting of hydroxylamine and salts thereof with '2-(3'- carbomethoxy-propylidene) -3-keto 4 benzamido-tetrahydrothiophene to produce the corresponding 3-isonitroso compound.

18. The process which comprises reacting a substance selected from the class consisting of hydroxylamine and salts thereof with 2-(5- carboethoxy-pentylidene) -3-keto-4 benzamidotetrahydrothiophene to produce the corresponding 3-isonitroso compound.

STANTON A. HARRIS. KARL FOLKERS.

REFERENCES CITED The following references are of record in the file of this patent:

Whitmore: Organic Chemistry, page 241, Van Nostrand, New York, 1937.

Certificate of Correction Patent No. 2,460,224. January 25, 1949.

STANTON A. HARRIS ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 13, for that portion of the formula reading HO OH read HC'-O'H; column 2, line 51, for yields as, read yields an; column 4, line 37, Example 2, for 2-4 read 2(4' and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 7th day of June, A. D.,1949.

moms F. MURPHY,

Am'stant Commissioner of Patents. 

